1. Field of the Invention
The present invention relates to an engine using compressed natural gas (CNG) as fuel, and more particularly, to an independent fuel injection system of a CNG engine, which includes an injector installed in an intake manifold and injecting fuel to each cylinder.
2. Description of Related Art
In general, CNG fuel exhibits higher combustion efficiency and generates a smaller amount of air contaminant than other vehicle fuels such as gasoline and diesel.
A vehicle engine system according to the related art, using the above-described CNG as fuel, generally includes a turbocharger, an intercooler, an injector, a mixer, and a throttle body. The turbocharger compresses intake air from outside to improve volume efficiency. The intercooler cools down boosted intake air which is discharged from the turbocharger. The injector injects CNG fuel. The mixer mixes the CNG injected from the injector with the intake air discharged from the intercooler. The throttle body supplies the mixture gas, containing the air and fuel mixed by the mixer, to the engine.
The mixture gas introduced through the throttle body is supplied to each cylinder of the engine and ignited by an ignition coil installed in the cylinder. The ignition operation of the ignition coil is controlled by an ignition control device. The ignition control device is connected to an engine control unit (ECU) so as to receive a control signal from the ECU, and a boost control valve is provided to control a boost of the intake air introduced to the turbocharger.
In the above-described CNG engine according to the related art, a cylinder head and an intake manifold have no partition wall for partitioning the introduction of mixture gas to each cylinder formed in a cylinder block, but the entire mixture gas is introduced into one entrance of the cylinder head.
Accordingly, multi-point injection may not be applied, and fuel injection to each cylinder and control for the fuel injection cannot be performed because there is no partition wall. Further, the mixture gas introduced into one entrance may be introduced into another cylinder.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.